How shooting whales with air rifles helps scientists study Antarctica’s changing environment

When you think about the work of a marine biologist, whale shooting may not be the first image that comes to mind.

But for Susan Bengtson Nash of Griffith University ‘s Humpback Whale Sentinel Program, a rifle is a key tool in her fieldwork arsenal.

Here’s how she and her colleagues collect samples from humpback whales:

“We shoot [modified darts] at the place of the whale’s back [and] recalling the dart causes it to kick, “says Professional Professor Bengtson Nash.

The darts penetrate the skin of the whales and buzzards, collecting the samples, before kicking back into the water where they sail until the researchers collect them.

The samples provide important information about the health of the Antarctic sea ice ecosystem, which the Humpback Whale Sentinel Program aims to monitor.

Overcoming the challenges of Antarctic exploration

A scientist is holding a small pink sample of a whale blubber.
Researchers look at the size of fat cells and their chemical combination.(Presented by: Susan Bengtson Nash)

But it is very difficult to carry out a scientific study in an environment that was once so precious at Antarctica: the number of scientists allowed to visit each year is limited, the weather is extremely bad, and it is expensive.

In 2020, the number of researchers visiting was particularly low due to the COVID-19 pandemic.

As a result, there will be gaps in their data in some research projects – a full year or more where they have no ideas.

To get around these problems, researchers in the Sentinel Whale Program collect samples of whales from crocodiles while migrating north.

Humpback whales spend the summer feeding in Antarctic waters before moving north to breeding grounds in warmer waters.

So, every winter Dr. Bengtson Nash and colleagues in places like Colombia, New Caledonia, Brazil and Western Australia have been visiting whale breeding sites in their local area to collect samples.

These samples serve as a surrogate for what is going on in the southern frigid waters.

The size of fat cells and pollutants will inform the health of whales

The team now has 13 consecutive years of whale data from donors to the program.

And while the individual blubber samples are small, the amount of information they can deliver is quite large.

For example, the size of the fat cells in the lump shows how much energy the whales have had in the summer of Antarctica.

A young whale jumps out of the water.
Researchers are looking at the number of female calves and young in the migrating population.(Presented by: Susan Bengtson Nash)

Analysis of isotopes and fatty acids gives information about where their food came from – mainly krill.

And the accumulation of persistent organic pollutants is also used as a measure of the fat content of the whales in a reserve.

At the same time, steroid hormones can be used to identify the number of pregnant women who are undergoing migration, according to Dr. Bengtson Nash.

“If they’re low on food sources, the women seem to be thinking ‘I’m not going to migrate this year, I’m going to live where the food is’, “she says.

Whale health indicators changing sea ice

The researchers linked their study of whale blubber to environmental data collected in Antarctica itself.

And they found evidence that humpback whales are “sentinels of a powerful Antarctic sea ice ecosystem”.

Packing away whale samples
Colleague Dr. Bengtson Nash will be packing away samples of their lab that they acquired from New Caledonia in January.(Presented by: Susan Bentson Nash)

“It was the first signal we got in 2010/11 – it was the strongest La Nina event on record,” says Dr Bengtson Nash.

There was less sea ice and phytoplankton changes in whale feeding grounds.

After that season, the whales came up in poor body condition, and seemed to be changing diet.

“They seemed to have moved away from the Antarctic krill,” Dr. Bengtson Nash says.

A large iceberg surrounded by floating ice.
Researchers say they have seen a correlation between low sea ice and poor whale health.(Presented by: Susan Bengtson Nash)

The next strong indication was that Antarctica had experienced very bad weather six years later.

“So let’s go back to our environmental data and oh look, 2017 was the worst year ever for sea ice,” says Dr Bengtson Nash.

Since then summer temperatures have worsened, exceeding 20 degrees Celsius on the Antarctic peninsula for the first time in 2019/20.

Researchers are not sure how badly sea ice levels are linked to poor whale health, but some say krill plays a major role.

Krill’s main role in Antarctica

Research has shown that krill larvae use sea ice to provide shelter from predators and as a means of transportation to food-rich waters, meaning that their spread is expected to change as sea ice is reduced.

So Kawaguchi, a krill ecologist with Australia’s Antarctic program, says climate change conditions predict that the northern region of krill will go south as warm waters.

Close-up of Antarctic krill.
Although small in their own right, the total mass of Antarctic krill is estimated to be larger than that of humans on the planet.(Presented by: Antarctic Division of Australia)

Dr Bengtson Nash says that while humpback whales in the Northern Hemisphere appear to have the potential to adapt to life without krill, a krill disaster could have a major impact on the Antarctic ecosystem. -full.

“Antarctic krill is what we call the main species. Everything depends on krill,” she says.

According to Dr. Kawaguchi, scientists believe that krill biofuels are equivalent to the total weight of humans on the planet.

“You can easily imagine how the dynamics of this same species could spread through the entire South Sea ecosystem,” he says.

As well as being a food source for the whales, Antarctic krill help capture atmospheric carbon dioxide, he said.

“Krill eats a lot of phytoplankton and turns them into fast-sinking concealed bullets.”

Scientists are still trying to figure out how climate change will affect krill numbers, and the effects are likely to change regionally.

According to Dr. Kawaguchi, however, it will not be bad news.

“I think the ecosystem is sustainable, so the system will change to a new standard, but its structure will definitely change – there may be winners and losers,” he says. saying.

Dr Bengtson Nash believes the crofts could change, but they could be canisters in the coal mine for bigger changes in the south.